Within recent years, a world-wide scarcity of natural resources has become a reality. This scarcity has made it necessary to recycle scrap articles and reuse them as raw materials. Within recent years, recycled paper stock has become increasingly important to the paper industry. Unfortunately, the recycling of a high-grade paper stock pulp is often frustrated by fabricating materials which were previously employed in their manufacture. Water-insoluble, hot-melt adhesives (such as presently employed in the manufacture of corrugated, cardboard, bags, books, etc.) are typical fabricating materials which cannot be effectively and economically removed from the recycled paper stock. Scrap paper articles contaminated with these water-insoluble, hot-melt adhesives are usually disposed of as wastes or employed in very low quality paper articles.
To be suitably adapted for its intended use, a hot-melt adhesive should possess a plurality of prerequisital properties. In general, the hot-melt adhesives should have: a relatively high melting point, sufficient flow characteristics to be effectively deposited upon the paper stock, suitably adapted to high speed fabrication equipment such as presently employed in the industry, compatibility and adhesiveness to the paper stock and have a relatively short set period. Such paper stock containers also necessitate an adhesive bond which can withstand a broad spectrum of physical, environmental and chemical abuses such as normally encountered during the shipment and storage thereof. Such containers are frequently exposed to a host of physical stresses (e.g., tearing, shearing, compression, impact, tension, etc.). The hot-melt adhesive should have sufficient durability to withstand these physical abuses. Divergent environmental conditions such as normally encountered by their usage in the trade also place further performance demands upon the required functional attributes of these adhesives. The hot-melts are normally required to retain their functional attributes under diverent humidity and thermal conditions (e.g., sub-zero to tropical, and arid to extremely humid conditions). The packaged contents as well as environmental conditions necessitate a hot-melt adhesive formulation which possesses adequate resistance against chemical degradation.
In U.S. Pat. No. 3,753,944 by J. Sirota et al., water-soluble, hot-melt adhesives comprised of blends of polyethylene oxides and polyalkylene oxides are disclosed. British Pat. No. 1,291,016 discloses a hot-melt adhesive comprised of a tall oil resin and/or colophony resins with surface-active polyethylene oxide adducts having an HLB Griffin value of 10-20. As in U.S. Pat. No. 3,753,944, the British patent discloses these water-soluble, hot-melt adhesives as being easily removable with water. As a result, these water-soluble, hot-melt adhesives are generally employed for highly specific end uses. The water-soluble, hot-melt adhesives, however, are not deemed to be a suitable replacement for the insoluble adhesives because of their inherent instability under humid, wet or inclement conditions.
Heretofore the art has been relatively successful in providing the trade with hot-melt hot-mel adhesives which meet the aforementioned physical and chemical requirements. In fulfilling these requirements, the commercially available, water-insoluble, hot-melt adhesives inherently impair effective recovery of high grade paper pulp stocks from paper scraps contaminated therewith. A water-insoluble, hot-melt adhesive which could be effectively and economically removed from scrap paper stock under existing alkali repulping technology would provide an additional, high-grade paper pulp source for the trade. A need also exists for insoluble, hot-melt additive compositions which can be readily converted to a water-soluble salt form and thus fulfill the aforementioned specialty uses. Such a hot-melt additive would possess a dual functionality heretofore not feasible with the existing hot-melt additives.